The subject matter of the present invention is a method of extracting and measuring a product from a bulk stock.
The present invention also relates to a method of adding one or several additives, extracted from a bulk stock, to a product contained in a hopper which feeds some sort of processing or distributing device, as well as the devices for putting it into effect.
It is essential in industry to be able to obtain delivery of quantities of products in accordance with a regular, pre-determined cycle. This is particularly the case in the plastics processing industry, where small grain or powdered additives have to be added to the basic material in very small quantities; said additives may, for example, be colouring pigments.
For this purpose, methods and devices have been recommended which make use of superimposed perforated surfaces working on the lock-gate principle with a measuring lock which fills and empties according to the relative movements of said surfaces.
However, the devices made up to now have not made it possible to obtain regularly the measurement and extraction of constant quantities of product, notably in the case of very small quantities of certain powdered or granulated products. The main difficulty encountered in this type of operation lies in obtaining a regular cycle of additions and constant proportions, which avoids constant monitoring of distribution or product processing equipment as well as handling and trial-and-error settings, which are a source of manufacturing rejects.
Another difficulty encountered in this type of operation relates to the nature and structure of the products or additives to be measured and added to the basic product.
In fact, these additives are delivered into the processing machine or its feed hopper and in some cases these products, notably powdered pigments for colouring plastics, cause considerable soiling, therefore the equipment has to be cleaned frequently and particularly every time a product different from the previous one is to be processed therein or an additive different from and unsuitable to coexist with the previous one is to be used.
Moreover, these powdered products have a tendency to lump and clog the extraction aperture(s) or to slide under the extraction components, wich affects their working and causes imperfect measuring and extraction.